The field of the invention is treatment of ischemia-reperfusion injury and inflammation.
Nitric oxide (NO) is a cell membrane-permeable, free radical molecule which accounts for the vasodilator activity of endothelium-derived relaxing factor (reviewed in Schmidt et al., Cell 78:919-925 [1994]). NO interacts with several intracellular molecular targets, one of which is soluble guanylate cyclase (sGC). Binding of NO to the heme group in sGC stimulates the conversion of guanosine triphosphate (GTP) to guanosine-3xe2x80x2,5xe2x80x2-cyclic monophosphate (cGMP). cGMP exerts it effects on cells, in part, through its action on cGMP-dependent protein kinase (cGDPK). Additional cGMP targets include cGMP-gated ion channels and cGMP-regulated cyclic nucleotide phosphodiesterases. Phosphodiesterases (PDEs) inactivate cGMP by converting it to GMP. At least four types of PDEs appear to participate in the metabolism of cyclic nucleotides in non-ocular tissues (types 1-3 and 5), only one of which, type 5 (PDE5), is specific for cGMP metabolism. Several agents act as selective inhibitors of PDE5, including dipyridamole and Zaprinast(trademark).
The biological effects of NO are also mediated by cGMP-independent mechanisms. NO can serve as an antioxidant, opposing the effect of superoxides. The antioxidant properties of NO appear to account for its ability to modulate proinflammatory activation of endothelial cells. NO may also react with superoxide to form peroxynitrite which may be responsible for the cellular toxicity associated with high levels of NO production.
NO decreases the adherence and aggregation of platelets exposed to a variety of stimuli. This has been demonstrated in vitro and in vivo (Adrie et al., Circulation 94:1919-1926 [1996]). The effect of NO on platelet function appears to be mediated by cGMP and is augmented by PDE5 inhibitors (see PCT application WO96/25184, which is incorporated herein by reference).
The use of NO as a drug is complicated by evidence suggesting that high levels of NO can contribute to cell injury (Nicholson et al., Trends Pharmacol Sci 12:19-27 [1991]). This is, at least in part, mediated by the combination of NO with reactive oxygen intermediates to form peroxynitrite which decomposes to toxic NO2+ and OHxe2x88x92. NO contributes to neuronal cell injury associated with cerebral ischemia (Iadecola, Trends Neurosci 20:132-139 [1997]). In addition, NO inhibits myocardial contractility and stimulates apoptosis of cardiac myocytes (Wu et al., J Biol Chem 272:14860-14866 [1997]), thereby impairing cardiovascular function. NO also contributes to inflammation in arthritis and possibly other autoimmune diseases when present at the site of inflammation (Nicholson et al., Id.).
NO inhibits adherence of neutrophils to endothelium, an effect which may depend on mast cells (Niu et al., Circ Res 79:992-999 [1996]).
It has been discovered that inhaled gaseous nitric oxide can act on both platelets and leukocytes, affecting them in a way that leaves them less likely to be activated once they reach a tissue susceptible to inflammation. The effect on platelets and leukocytes presumably occurs while they are in the pulmonary circulation, since NO itself is rapidly inactivated by hemoglobin once it contacts the blood (Rich et al., J Appl Physiol 75:1278-1284 [1993] and Rimar et al., Circulation 88:2884-2887 [1993]) and so likely does not travel to distal sites of inflammation.
Accordingly, the invention relates to a method for lessening or preventing non-pulmonary ischemia-reperfusion injury in a mammal. The method includes identifying a mammal (e.g., a human) that has ischemia-reperfusion or is at risk for developing ischemia-reperfusion in a non-pulmonary tissue, and causing the mammal to inhale a therapeutically effective amount of gaseous nitric oxide. This amount is sufficient to diminish the ability of circulating leukocytes or platelets to become activated and contribute to an inflammatory process at the site of ishemia-reperfusion in the non-pulmonary tissue. This lessens or prevents non-pulmonary ischemia-reperfusion injury in the mammal. In combination with the inhaled NO gas, the mammal can be administered a therapeutically effective amount of a second compound that potentiates the therapeutic effect of gaseous NO. The second compound can be, for example, a phosphodiesterase inhibitor (e.g., 2-o-propoxyphenyl-8-azapurin-6-one [Zaprinast(trademark)], dipyridamole, theophylline, sildenafil [Viagra(trademark), Pfizer], or 1,3-dimethyl-6-[2-propoxy-5-methanesulphonylamidophenyl]-pyrazolo[3,4-D]pyrimidin-4-[5H]-one) or superoxide dismutase. The second compound can alternatively be an antithrombotic agent such as ticlopidine, streptokinase, urokinase, t-PA or an analog thereof (e.g., met-t-PA, Retevase(trademark), or FE1X), heparin, hirudin or an analog thereof (e.g., Hurulog(trademark)), non-steroidal anti-inflammatory agent (e.g., indomethacin or aspirin), a glucocorticoid (e.g., prednisone), or a cytotoxic agent (e.g., methotrexate); or an anti-leukocyte agent such as an anti-leukocyte antibody.
The method is used to treat or prevent ischemia-reperfusion injury including those caused by surgery (e.g., transplantation surgery [especially kidney or heart transplantation surgery] or heart bypass surgery), thrombolysis, stroke, trauma-induced temporary hypotension, or a vascular interventional procedure such as atherectomy or angioplasty including the use of a laser, balloon, or stent. The method can be used to treat or prevent ischemia-reperfusion injury after percutaneous transluminal coronary angioplasty. The injury treated or prevented can occur in any non-pulmonary tissue, including the kidney, heart, or brain.
The invention also features a method for decreasing or preventing non-pulmonary inflammation in a mammal. Examples of non pulmonary inflamation are arthritis, myocarditis, encephalitis, transplant rejection, systemic lupus erythematosis, gout, dermatitis, inflammatory bowel disease, hepatitis, or thyroiditis. This method includes the steps of identifying a mammal which has existing inflammation or is at risk for developing inflammation in a non-pulmonary tissue; causing the mammal to inhale a therapeutically effective amount of gaseous nitric oxide sufficient to diminish the ability of circulating leukocytes or platelets to become activated in a manner that contributes to an inflammatory process in the non-pulmonary tissue, thereby decreasing or preventing non-pulmonary inflammation in the mammal; and administering to the mammal a therapeutically effective amount of a second compound that potentiates the anti-inflammatory effect of inhaled gaseous nitric oxide. The second compound can be a phosphodiesterase inhibitor (e.g., 2-o-propoxyphenyl-8-azapurin-6-one [Zaprinast(trademark)], dipyridamole, theophylline, sildenafil [Viagra(trademark), Pfizer], or 1,3-dimethyl-6-[2-propoxy-5-methanesulphonylamidophenyl]-pyrazolo[3,4-D]pyrimidin-4-[5H]-one) or superoxide dismutase. The second compound can alternatively be an anti-inflammatory drug such as a non-steroidal anti-inflammatory agent (e.g., indomethacin or aspirin), a glucocorticoid (e.g., prednisone), or a cytotoxic agent (e.g., methotrexate).
The NO gas inhaled by the mammal in the method of this invention can be administered at a predetermined concentration. Preferably it is administered in the absence of tobacco smoke. Preferably the predetermined concentration is 0.1 ppm to 300 ppm, more preferably 1 ppm to 250 ppm, and most preferably 5 ppm to 200 ppm. NO can be inhaled continuously or intermittently for an extended period, i.e., for at least 24 hours.
As used herein xe2x80x9cpreventingxe2x80x9d an injury means preventing at least part of the injury, and does not imply that 100% of the injury is prevented. Injury prevented is ischemia-reperfusion injury or inflammation. As used herein, injury xe2x80x9coccurs spontaneously,xe2x80x9d means that the injury has no readily observable cause.
As used herein, xe2x80x9cpotentiating the therapeutic effect of gaseous nitric oxide,xe2x80x9d (by a second compound) means increasing the duration or magnitude of the effect.
As used herein, xe2x80x9cvascular interventional procedurexe2x80x9d means any surgical procedure that involves an anatomical disruption or a mechanical disturbance of a blood vessel.
Other features and advantages of the present invention will be apparent from the following detailed description and also from the claims.